Examples of optical window in the following topics:
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- Visible wavelengths pass through the "optical window", the region of the electromagnetic spectrum which allows wavelengths to pass largely unattenuated through the Earth's atmosphere (see opacity plot in.
- The optical window is also called the visible window because it overlaps the human visible response spectrum.
- A consequence of the existence of the optical window in Earth's atmosphere is the relatively balmy temperature conditions on Earth's surface.
- The Sun's luminosity function peaks in the visible range and light in that range is able to travel to the surface of the planet unattenuated due to the optical window.
- This is again not coincidental; the light in this range is the most plentiful to organisms on the surface of Earth because the Sun emits about half of its luminosity in this wavelength range and it is allowed to pass freely through the optical windows in Earth's atmosphere.
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- Visible light passes relatively unimpeded through the atmosphere in the "optical window."
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- Now let's move the material in a position the blocks our window to the enclosure.
- We know that as light travels through the material the intensity field should approach the source function but we also know that the light emerging from the window must have $I_\nu=B_\nu(T)$.
- A thermal emitter has $S_\nu = B_\nu(T)$,$B_\nu(T)$ so the radiation field approaches $B_\nu(T)$ (blackbody radiation) only at large optical depth.
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- A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback.
- A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback (usually an optical cavity).
- When a gain medium is placed in an optical cavity, a laser can then produce a coherent beam of photons.
- The gain medium is where the optical amplification process occurs.
- The most common type of laser uses feedback from an optical cavity--a pair of highly reflective mirrors on either end of the gain medium.
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- At $t=t_0$ the sphere is optically thin.
- What is the total luminosity of the sphere as a function of $M_0, R(t)$ and $T_0$while the sphere is optically thin?
- What is the luminosity of the sphere as a function of time after it becomes optically thick in terms of $M_0, R(t)$ and $T_0$?
- Give an implicit relation in terms of $R(t)$ for the time $t_1$ when the sphere becomes optically thick.
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- In this section we will discuss both optical and electron microscopy.
- You have probably used an optical microscope in a high school science class.
- In optical microscopy, light reflected from an object passes through the microscope's lenses; this magnifies the light.
- Although this type of microscopy has many limitations, there are several techniques that use properties of light and optics to enhance the magnified image:
- Electron microscopes use electron beams to achieve higher resolutions than are possible in optical microscopy.
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- In optical imaging, there is a fundamental limit to the resolution of any optical system that is due to diffraction.
- However, there is a fundamental maximum to the resolution of any optical system that is due to diffraction (a wave nature of light).
- An optical system with the ability to produce images with angular resolution as good as the instrument's theoretical limit is said to be diffraction limited.
- The denominator $nsin \theta$ is called the numerical aperture and can reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
- There are techniques for producing images that appear to have higher resolution than allowed by simple use of diffraction-limited optics.
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- Optical discs are digital storing media read in an optical disc drive using laser beam.
- Compact disks (CDs) and digital video disks (DVDs) are examples of optical discs.
- They are read in an optical disc drive which directs a laser beam at the disc.
- In this early version of an optical disc, you can see the pits and lands which either reflect back light or scatter it.
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- At $t=t_0$ the sphere is optically thin.
- What is the total luminosity of the sphere as a function of $M_0, R(t)$ and $T_0$ while the sphere is optically thin?
- What is the luminosity of the sphere as a function of time after it becomes optically thick in terms of $M_0, R(t)$ and $T_0$?
- Give an implicit relation in terms of $R(t)$$t_1$ for the time $t_1$ when the sphere becomes optically thick.
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- We are particularly interested in the form of the spectrum from a power-law distribution of particles for frequencies where the region is optically thick.
- We know from the formal solution of radiative transfer that the spectrum approaches the source function at large optical depth.
- Because the optically thin emission spectrum increases more slowly with frequency than the source function (or even decreases), we expect synchrotron absorption to be important at low frequencies where the the integrated optically thin emission exceeds the source function.